Portable audio device having reduced sensitivity to RF interference and related methods

ABSTRACT

A portable audio device having reduced sensitivity to RF interference over a predetermined frequency range from an adjacent mobile wireless communications device may include a portable housing, a battery carried thereby, a recharging power input connected to the battery, a digital signal input, and an audio analog signal output. A digital-to-analog converter (DAC) may be carried by the portable housing and powered by the battery for converting a selected digital audio file from a memory into an analog audio signal. An audio analog amplifier may be connected between the DAC and the audio analog signal output. A first RF filter(s) may be connected to the recharging power input, and a second RF filter(s) may be connected to the audio analog signal output, both for reducing RF interference over the predetermined frequency range from the adjacent mobile wireless communications device.

RELATED APPLICATION

This application is a continuation of Ser. No. 11/343,090 filed Jan. 30,2006, now U.S. Pat. No. 7,616,973 the entire disclosure of which ishereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to the field of electronic devices, and,more particularly, to portable audio devices and related methods.

BACKGROUND OF THE INVENTION

Cellular communications systems continue to grow in popularity and havebecome an integral part of both personal and business communications.Cellular telephones allow users to place and receive voice calls mostanywhere they travel. Moreover, as cellular telephone technology hasincreased, so too has the functionality of cellular devices and thedifferent types of devices available to uses. For example, many cellulardevices now incorporate personal digital assistant (PDA) features suchas calendars, address books, task lists, etc. Moreover, suchmulti-function devices may also allow users to wirelessly send andreceive electronic mail (email) messages and access the Internet via acellular network and/or a wireless local area network (WLAN), forexample.

Accordingly, because of the widespread use and reliance on cellulardevices, many users carry their cellular devices on their person much ofthe day. Yet, since cellular devices are frequently communicating with acellular network even when a user is not participating in a phone call,they are frequently emitting radio frequency (RF) signals. When in closeproximity to other electronic equipment, such as personal audio devices(e.g., portable radios, MP3 players, etc.), these RF signals may causeinterference which results in an audible buzz or other undesirable soundfrom the personal audio device.

One exemplary portable audio device is disclosed in U.S. patentapplication publication no. 2003/0059071. This application is directedto an integrated personal audio device that provides hearing protectionfor a user. The device includes a flexible band configured to extend atleast partially around a head of a user. An audio transmitter is coupledto the band. The band has two legs that terminate at respective endportions. Each end portion is coupled to an audio speaker, which iselectrically connected to the audio transmitter. A hearing protector ismounted onto each respective audio speaker. Moreover, the audiotransmitter may include RF shielding to filter radio interferenceassociated with nearby electric equipment, for example.

While such devices may provide some reduction in unwanted RFinterference, further RF interference protection may be required tosignificantly mitigate the effects of RF interference from a nearbycellular device, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a portable audio device havingreduced sensitivity to RF interference from an adjacent mobile wirelesscommunications device according to the invention.

FIG. 2 is a schematic block diagram of an alternate embodiment of theportable audio device of FIG. 1.

FIG. 3 is front view of the portable audio device of FIG. 2 illustratinga display and user input device thereof.

FIG. 4 is a schematic diagram of the recharging power input circuit andassociated first RF filter elements of FIG. 2.

FIG. 5 is schematic diagram of the stereo headphone audio analog signaloutput circuit and associated second RF filter elements of FIG. 2.

FIG. 6 is a schematic block diagram of the line input digital signalinputs and associated third RF filter elements of FIG. 2.

FIG. 7 is a schematic diagram of the line out audio analog signal outputcircuit and associated second RF filter elements of FIG. 2.

FIG. 8 is a schematic block diagram of the microphone audio analog inputcircuit and associated fourth filter elements of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present description is made with reference to the accompanyingdrawings, in which preferred embodiments are shown. However, manydifferent embodiments may be used, and thus the description should notbe construed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete. Like numbers refer to like elements throughout, and primeand multiple prime notation are used to indicate similar elements inalternate embodiments.

Generally speaking, a portable audio device is disclosed herein havingreduced sensitivity to RF interference over a predetermined frequencyrange from an adjacent mobile wireless communications device. Theportable audio device may include a portable housing, a battery carriedby the portable housing, a recharging power input connected to thebattery, a digital signal input, and an audio analog signal output. Theportable audio device may further include a memory carried by theportable housing and powered by the battery for storing digital audiofiles input thereto via the digital signal input. In addition, adigital-to-analog converter (DAC) may be carried by the portable housingand powered by the battery for converting a selected digital audio filefrom the memory into an analog audio signal. Moreover, an audio analogamplifier may be connected between the DAC and the audio analog signaloutput. At least one first RF filter may be connected to the rechargingpower input for reducing RF interference over the predeterminedfrequency range from the adjacent mobile wireless communications device.Additionally, at least one second RF filter may be connected to theaudio analog signal output for reducing RF interference over thepredetermined frequency range from the adjacent mobile wirelesscommunications device.

More particularly, the portable audio device may further include atleast one third RF filter connected to the digital signal input forreducing RF interference over the predetermined frequency range from theadjacent mobile wireless communications device. By way of example, theat least one third RF filter may be a parallel connected capacitor. Theportable audio device may also include an audio analog input connectedto the audio analog amplifier, and at least one fourth RF filterconnected to the audio analog signal input for reducing RF interferenceover the predetermined frequency range from the adjacent mobile wirelesscommunications device. The at least one fourth RF filter may include aseries connected inductor and a parallel connected capacitor, forexample.

By way of example, the at least one first RF filter may include aparallel connected capacitor, and the at least one second RF filter mayinclude a series connected inductor and parallel connected capacitor. Inaddition, the predetermined frequency range may be from about 30 MHz to6 GHz, for example. Also, the stored digital audio files may be digitalstereo audio files, MP3 files, etc. Moreover, the portable audio devicemay further include at least one display carried by the portablehousing, and at least one user input device carried by the portablehousing.

A related method aspect is for reducing sensitivity of a portable audiodevice, such as the one described briefly above, to RF interference overa predetermined frequency range from an adjacent mobile wirelesscommunications device. The method may include connecting at least onefirst RF filter to the recharging power input for reducing RFinterference over the predetermined frequency range from the adjacentmobile wireless communications device, and connecting at least onesecond RF filter to the audio analog signal output for reducing RFinterference over the predetermined frequency range from the adjacentmobile wireless communications device.

Referring initially to FIG. 1, a portable audio device 20 advantageouslyhas reduced sensitivity to RF interference over a predeterminedfrequency range from RF electromagnetic (EM) energy 21 from an adjacentmobile wireless communications device 22. In particular, the RF signalstransmitted by the mobile wireless communications device 22 are withinone or more predetermined frequency ranges or bands, as will beappreciated by those skilled in the art. These transmissions can causeinterference at the portable audio device 20 that results in undesirableaudible noises, such as buzzing, for example. As will be describedfurther below, the portable audio device 20 advantageously includes aplurality of RF filters to reduce the sensitivity of the device to suchclose-proximity RF interference from the EM energy emanating from themobile wireless communications device 22.

The portable audio device 20 illustratively includes a portable housing23, a battery 24 carried by the portable housing, a recharging powerinput 25 connected to the battery, a digital signal input 26, and anaudio analog signal output 27. The digital signal input 27 may be auniversal serial bus (USB) 2.0 input, for example, which allows theportable audio device to be connected to a personal computer (PC) todownload digital audio files (e.g., digital stereo files, MP3 files,etc.) to be stored in a memory 30. The recharging power input 25 may beconnected to a DC power adapter, for example. In some embodiments, therecharging power input 25 may be connected to the voltage line of theUSB port so that the device 20 is charged when connected to a PC orother USB host, for example. The audio analog signal output may be aheadphone output and/or stereo line outs for connection to a separateaudio system, etc., for example. Of course, other suitableinputs/outputs may be used in some embodiments, as will be appreciatedby those skilled in the art.

The portable audio device 20 also illustratively includes adigital-to-analog converter (DAC) 31 carried by the portable housing 23and powered by the battery 24 for converting a selected digital audiofile from the memory 30 into an analog audio signal, as will beappreciated by those skilled in the art. Moreover, one or more audioanalog amplifiers 32 is illustratively connected between the DAC 31 andthe audio analog signal output 27. The audio analog amplifier(s) 32amplifies the analog output signals to the appropriate level for aheadphone or stereo line out, for example, as will be appreciated bythose skilled in the art.

At least one first RF filter 33 is illustratively connected to therecharging power input 25 for reducing the RF interference over thepredetermined frequency range or ranges of interest from the adjacentmobile wireless communications device 22. By way of example, thepredetermined frequency range may be from about 30 MHz to 6 GHz.Additionally, at least one second RF filter 34 is illustrativelyconnected to the audio analog signal output 27 also for reducing the RFinterference over the predetermined frequency range from the adjacentmobile wireless communications device 22. The recharging power input 25and audio analog signal output 27 are particularly susceptible to the RFinterference. Yet, by matching the RF filters 33, 34 to a predeterminedfrequency range or ranges typically associated with a cellular or otherwireless communications device (e.g., personal area network (PAN), WLANdevice, etc.) that may be in close proximity to the portable audiodevice 20, the overall sensitivity of the device may be significantlyreduced to provide an improved user experience.

Turning now additionally to FIG. 2, further aspects are now describedwith reference to a portable audio device 20′ which illustrativelyincludes at least one third RF filter 35′ connected to the digitalsignal input 26′ also for reducing RF interference over thepredetermined frequency range from the adjacent mobile wirelesscommunications device 22. In the illustrated embodiment, the digitalsignal input 26′ has stereo line inputs. Furthermore, the audio analogsignal output comprises a stereo headphone output 27 a′ and stereo lineoutput 27 b′, each of which has a respective filter element 34 a′, 34 b′and audio analog amplifiers 32 a′, 32 b′.

The portable audio device 20′ also illustratively includes an audioanalog input 36′, such as a microphone input, connected to the audioanalog amplifiers 32 a′, 32 b′. At least one fourth RF filter 37′ isfurther connected to the audio analog signal input 36′ again forreducing RF interference over the predetermined frequency range from theadjacent mobile wireless communications device 22.

Referring additionally to FIG. 3, the portable audio device 20′ furtherillustratively includes a display 38′ carried by the portable housing23′, and a user input device (i.e., buttons 39′) also carried by theportable housing. A controller or processor (not shown) may cooperatewith the buttons 39′ and the display 38′ to allow a user to selectdigital audio files (e.g., songs, etc.) to be converted to audio signals(i.e., played) from a menu on the display, as will be appreciated bythose skilled in the art. In the illustrated example, “Song 2” isselected from among the listed songs. Of course, other types of userinput devices may be used instead of or in addition to the buttons 39′,such as a touch screen, scroll wheels, track balls, etc., as will alsobe appreciated by those skilled in the art. Moreover, it should be notedthat the portable audio device 20′ may also be used for displayingdigital images and/or video, as will also be appreciated by thoseskilled in the art.

The portable audio device 20′ also illustratively includes respectiveconnectors/plugs 40′-44′ for the recharging power input 25′, digitalsignal input 26′, audio analog input 36′, and audio signal outputs 27a′, 27 b′, as will be appreciated by those skilled in the art. Otherfeatures and components common to portable audio devices such as MP3players and portable radios which are well known to those of skill inthe art may also be included.

Turning now to FIGS. 4-8, particular examples of the above-noted RFfilters are now described. The recharging power input circuit 25′includes digital voltage inputs DBVDD and DCVDD connected to theappropriate power supplies (e.g., 1.42 or 3.3V), a digital ground inputDGND, an analog voltage input AVDD connected to a 3.3V source, an analogground AGND, and an additional voltage input HPVDD connected to a 3.3Vsource and associated ground HPGND. The first RF filter 33′illustratively includes a capacitor C1 connected between the digitalvoltage input DBVDD and digital ground DGND (i.e., connected in parallelwith DBVDD), a capacitor C2 connected between the digital voltage inputDCVDD and digital ground DGND, a capacitor C3 connected between theanalog voltage input AVDD and analog ground AGND, and a capacitor C4connected between the additional voltage input HPVDD and associatedground HPGND. Furthermore, capacitors C5, C6 are connected in parallelwith the capacitor C1, capacitors C7, C8 are connected in parallel withthe capacitor C2, capacitors C9, C10 are connected in parallel with thecapacitor C3, and capacitors C11, C12 are connected in parallel with thecapacitor C4.

The stereo headphone output circuit 27 a′ illustratively includes a leftheadphone output LHPOUT and a right headphone output RHPOUT. The leftheadphone output LHPOUT has a series connected capacitor C20 and aparallel connected resistor R1 connected thereto, and the rightheadphone output similarly has a series connected capacitor C21 and aparallel connected resistor R2 connected thereto, as shown in FIG. 5.Moreover, the second RF filter 34 a′ illustratively includes a seriesconnected inductor L1 and a parallel connected capacitor C22 connectedto the left headphone output LHPOUT, and a series connected inductor L2and a parallel connected capacitor C23 connected to the right headphoneoutput RHPOUT as shown.

The stereo line input circuit 26′ illustratively includes a left lineinput LLINEIN and a right line input RLINEIN. A resistor R3 andcapacitor C31 are connected in series with the left line input LLINEIN,and a resistor R4 capacitor C30 are also connected in parallel with theleft line input. Similarly, a resistor R5 and capacitor C33 areconnected in series with the right line input RLINEIN, and a resistor R6and capacitor C32 are also connected in parallel with the right lineinput as shown in FIG. 6. The third RF filter 35′ illustrativelyincludes a capacitor C34 parallel connected to the left line inputLLINEIN, and a capacitor C35 parallel connected to the right line inputRLINEIN.

The stereo line output circuit 27 b′ illustratively includes a left lineoutput LOUT and a right line output R OUT (FIG. 7). A capacitor C40 andresistor R10 are series connected to the left line output LOUT, and aresistor R11 is also parallel connected to the left line output.Moreover, a capacitor C41 and resistor R12 are series connected to theright line output ROUT, and a resistor R13 is parallel connected to theright line output. The RF filter 34 b′ illustratively includes aninductor L10 series connected and a capacitor C42 parallel connected tothe left line output LOUT. The RF filter 34 b′ further illustrativelyincludes an inductor L11 series connected and a capacitor C43 parallelconnected to the right line output ROUT.

In addition, the microphone input circuit 36′ illustratively includes amicrophone input MICIN and a microphone bias input MICBIAS, as shown inFIG. 8. A capacitor C50 and resistor Rmic are series connected to themicrophone input MICIN, and a resistor R14 and capacitor C51 are alsoparallel connected to the microphone input. Furthermore, a resistor R15is series connected to the microphone bias input MICBIAS. The fourth RFfilter 37′ illustratively includes capacitors C52 and C53 parallelconnected to the microphone input MICIN, as well as a series connectedinductor L12 as shown.

It will be appreciated that the above noted the selection of theabove-noted filter components will be based upon the given frequencyband of interest, and the additional circuit components connected to thevarious inputs/outputs in a given embodiment. Moreover, it will also beappreciated by those skilled in the art that various circuits such asthe recharging power input circuit 25′, stereo headphone output circuit27 a′, stereo line input circuit 26′, stereo line output circuit 27 b′,and microphone input circuit 36′ may be implemented with an audiocoder/decoder (codec) chip, for example. Moreover, various componentsdiscussed above may be implemented using a combination of hardware andsoftware modules, as will also be appreciated by those skilled in theart.

A related method aspect is for reducing sensitivity of a portable audiodevice 20 to RF interference over a predetermined frequency range froman adjacent mobile wireless communications device 22. The method mayinclude connecting at least one first RF filter 33 to the rechargingpower input 25 for reducing RF interference over the predeterminedfrequency range from the adjacent mobile wireless communications device22. The method may further include connecting at least one second RFfilter 34 a′ to the audio analog signal output 27 a′ also for reducingRF interference over the predetermined frequency range from the adjacentmobile wireless communications device 22, as discussed further above.Additional method aspects will be appreciated from the foregoingdescription and need not be discussed further herein.

Many modifications and other embodiments will come to the mind of oneskilled in the art having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it isunderstood that various modifications and embodiments are intended to beincluded within the scope of the appended claims.

1. A portable electronic device comprising: a portable housing; abattery carried by said portable housing; a recharging power inputcoupled to said battery; a signal input; an audio signal output; amemory carried by said portable housing and powered by said battery forstoring audio files input thereto via said signal input; an audio analogamplifier powered by said battery and coupled between said memory andsaid audio signal output; at least one first RF filter coupled to saidrecharging power input; and at least one second RF filter coupled tosaid audio signal output.
 2. The portable electronic device of claim 1further comprising at least one third RF filter coupled to said signalinput.
 3. The portable electronic device of claim 2 wherein said atleast one third RF filter comprises a parallel coupled capacitor.
 4. Theportable electronic device of claim 1 further comprising: an audio inputcoupled to said audio analog amplifier; and at least one fourth RFfilter coupled to said audio input.
 5. The portable electronic device ofclaim 4 wherein said at least one fourth RF filter comprises a seriescoupled inductor and a parallel coupled capacitor.
 6. The portableelectronic device of claim 1 wherein said at least one first RF filtercomprises a parallel coupled capacitor.
 7. The portable electronicdevice of claim 1 wherein said at least one second RF filter comprises aseries coupled inductor and parallel coupled capacitor.
 8. The portableelectronic device of claim 1 wherein said at least one first and secondfilters each filters frequencies in a frequency range of from about 30MHz to 6 GHz.
 9. The portable electronic device of claim 1 wherein thestored audio files comprise digital stereo audio files.
 10. The portableelectronic device of claim 1 further comprising at least one displaycarried by said portable housing; and at least one user input devicecarried by said portable housing.
 11. A portable electronic devicecomprising: a portable housing; a battery carried by said portablehousing; a recharging power input coupled to said battery; a signalinput; an audio signal output; a memory carried by said portable housingand powered by said battery for storing digital stereo audio files inputthereto via said signal input; an audio analog amplifier powered by saidbattery and coupled between said memory and said audio signal output; atleast one first RF filter coupled to said recharging power input; atleast one second RF filter coupled to said audio signal output; and atleast one third RF filter coupled to said signal input.
 12. The portableelectronic device of claim 11 further comprising: an audio input coupledto said audio analog amplifier; and at least one fourth RF filtercoupled to said audio input.
 13. The portable electronic device of claim11 wherein said at least one first, second and third filters eachfilters frequencies in a frequency range of from about 30 MHz to 6 GHz.14. The portable electronic device of claim 11 further comprising atleast one display carried by said portable housing; and at least oneuser input device carried by said portable housing.
 15. A method forreducing sensitivity of a portable electronic device to RF interference,the portable electronic device comprising a portable housing, a batterycarried by the portable housing, a recharging power input coupled to thebattery, a signal input, an audio signal output, a memory carried by theportable housing and powered by the battery for storing audio filesinput thereto via the signal input, and an audio analog amplifiercoupled between the memory and the audio signal output, the methodcomprising: coupling at least one first RF filter to the rechargingpower input; and coupling at least one second RF filter to the audiosignal output.
 16. The method of claim 15 further comprising coupling atleast one third RF filter to the signal input.
 17. The method of claim16 wherein the at least one third RF filter comprises a parallel coupledcapacitor.
 18. The method of claim 15 wherein the portable audio devicefurther comprises an audio input coupled to the audio analog amplifier;and further comprising coupling at least one fourth RF filter to theaudio input.
 19. The method of claim 18 wherein the at least one fourthRF filter comprises a series coupled inductor and a parallel coupledcapacitor.
 20. The method of claim 15 wherein the at least one first RFfilter comprises a parallel coupled capacitor.
 21. The method of claim15 wherein the at least one second RF filter comprises a series coupledinductor and parallel coupled capacitor.
 22. The method of claim 15wherein the at least one first and second filters each filtersfrequencies in a range of from about 30 MHz to 6 GHz.
 23. The method ofclaim 15 wherein the stored digital audio files comprise digital stereoaudio files.
 24. The method of claim 15 wherein the portable electronicdevice further comprises at least one display carried by the portablehousing; and at least one user input device carried by the portablehousing.